How to use golang package

Golang is an efficient, fast and stable programming language that has received widespread attention and application in the field of software development. Compared with other languages, golang has many advantages, one of which is its rich standard library, which provides various tools and resources developers need. In this article, we will introduce golang’s packages in detail and how to use these packages.

What is golang package?

In golang, a package is a collection of related functions, types and variables, which plays an organizational structure in the code. Similar to libraries or modules in other languages, packages enable code reuse and modularization. All golang programs must use packages, and the import of packages can be declared at the head of the source code file.

How to use golang package?

Using golang packages requires three steps: importing the package, accessing the functions or variables in the package, and calling these functions or using these variables. These steps are demonstrated in the example below.

Example 1:

package main

import (
    "fmt"
    "math/rand"
)

func main() {
    fmt.Println("My favorite number is", rand.Intn(10))
}

In this example, we imported the fmt and math/rand packages. The program prints a random integer from 0 to 9. The rand.Intn function is used to obtain random numbers. After importing a package, we can access its functions and variables by its name. For example, we use rand.Intn to call the Intn function.

Example 2:

package main

import (
    "fmt"
    "net/http"
)

func main() {
    resp, err := http.Get("https://www.google.com")
    if err != nil {
        fmt.Println("Error:", err)
        return
    }
    defer resp.Body.Close()
    fmt.Println("Status:", resp.Status)
}

In this example, we imported fmt and net/http. This program gets the HTTP response from the Google website and prints the response status code. After importing a package, we can access its functions and variables by its name. For example, we use http.Get to call the Get function and resp.Status to access the response status.

How to create your own golang package?

We can also create our own golang package. The following are the steps to create your own package:

1. Create a package directory

We can create a golang package in any directory, but it is best to create it in our workspace directory tree it. Our workspace directory tree must contain the src directory, which contains all our go source files.

For example, we can create a new package directory under the workspace directory tree/src/myutils.

2. Put the function code into the package

We put our code into one or more .go files in the package directory. These files must be in the same directory as the package declaration.

For example, create a myutils.go file in the myutils directory and add the following code in it:

package myutils

import "fmt"

func SayHello() {
    fmt.Println("Hello, World!")
}

3. Use your own package in other code

us Our package can be used like any other package. We can import it using the import statement and then use its functions and variables.

For example, in our main program, we can use the following code:

package main

import "myutils"

func main() {
    myutils.SayHello()
}

On my computer, this program will print:

Hello, World!

Summary

In Golang, packages are a very important way of organizing code. They provide an important mechanism for modular, reusable, and easy-to-maintain code. When using Golang, you must use many common packages, such as fmt and io, as well as create new packages in your own code and encapsulate the functions and structures in a module for future development.

In addition, Go officially provides some very powerful packages, such as encoding, crypto, http, etc. Mastering the use of these packages will make development easier and more efficient. Therefore, learning to use Golang packages is one of the necessary skills to become a Golang developer.

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